• Journal of Communications and Networks
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• 제13권5호
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• pp.442-448
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• 2011

It's a challenging task to design a high performance modulation for satellite and space communications due to the limited power and bandwidth resource. Constant envelope modulation is an attractive scheme to be used in such cases for their needlessness of input power back-off about 2~3 dB for avoidance of nonlinear distortion induced by high power amplifier. The envelope of Feher quadrature phase shift keying (FQPSK) has a least fluctuation of 0.18 dB (quasi constant envelope) and can be further improved. This paper improves FQPSK by defining a set of new waveform functions, which changes FQPSK to be a strictly constant envelope modulation. The performance of the FQPSK adopting new waveform is justified by analysis and simulation. The study results show that the novel FQPSK is immune to the impact of HPA and outperforms conventional FQPSK on bit error rate (BER) performance. The BER performance of this novel modulation is better than that of FQPSK by more than 0.5 dB at least and 2 dB at most.

• Journal of Power Electronics
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• 제13권2호
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• pp.197-205
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• 2013

In energy injection resonant AC-AC converters, due to the low frequency effect of the AC input envelope and the low energy injection losses requirement, the constant and steady control of the high frequency AC output envelope is still a problem that has not been solved very well. With the aid of system modeling, this paper analyzes the mechanism of the envelope pit on the resonant AC current. The computing methods for the critical damping point, the falling time and the bottom value of the envelope pit are presented as well. Furthermore, this paper concludes the stability precondition of the system AC output. Accordingly, an optimal control method for the AC output envelope is put forward based on the envelope prediction model. This control method can predict system responses dynamically under different series of control decisions. In addition, this control method can select best series of control decisions to make the AC output envelope stable and constant. Simulation and experimental results for a contactless power transfer system verify the control method.

• 한국통신학회논문지
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• 제21권9호
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• pp.2470-2480
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• 1996

The energy efficiency and bandwidth efficiency are two important criterion in designing a modulation scheme Especially the constant envelope property must be considered as in the non-linear channel tht exit, for example in the nonlinear amplifiers for satellite repeater. The Q$^{2}$AM(Quadrature Quadrature Amplitude Modulation) is a new modulation scheme which combines the Q$^{2}$PSK(Quadrature Quadrature Phase Shift Keying) scheme which increases the signal space dimension and the QAM scheme which increases the bandwidth efficiency using the multi-level signal. The Q$^{2}$AM scheme has by far superior spectrum efficiency compared with the existing modulation schemes. Applying this scheme in the non-linear communication system increses the bandwidth efficiency but cannot envelop property. In this paper, a new system architecture is suggested which satisfies the large spectrum efficiency and constant envelope property by implementing the linear block coding prior to the Q$^{2}$AM modulation. the system has improved in performance by gaining the constant envelope and the additional coding gain. We able to observe the performance improvement of the suggested system(at BER=10$^{-5}$ ) of 4.4 dB for the 16-QAM and 0.7 dB for the Q$^{2}$PSK under the exact spectrum efficiency.

• 한국통신학회논문지
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• 제29권6A호
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• pp.683-689
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• 2004

The power and bandwidth efficient constant-envelope BPSK (CE-BPSK) modulation is proposed. The CE-BPSK signal is realized specifying the phase transition characteristics for the conventional low pass filtered BPSK signal. Since the CE-BPSK signal has constant envelope and modified waveform, the CE-BPSK signal has better power and bandwidth efficiency compared to the conventional BPSK signal while the CE-BPSK signal is backward compatible to the conventional BPSK signal. It is also shown that the bit error rate performance of the CE-BPSK signal is the same as that of the conventional BPSK signal.

• Journal of Positioning, Navigation, and Timing
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• 제10권4호
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• pp.335-340
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• 2021

A constant envelope multiplexing via constellation tailoring scheme is proposed for flexible power allocation of Global Navigation Satellite System (GNSS) signals. The proposed scheme is compared with the coherent adaptive subcarrier modulation (CASM) adopted in the L1 band signals of the Global Positioning System (GPS) in terms of power difference and power loss. Analysis of the constellation optimization results on the power difference and power loss show that the proposed scheme outperforms the CASM of the GPS signals in the allowable power difference of less than 0.1 dB.

• 한국정보통신학회논문지
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• 제15권10호
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• pp.2149-2156
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• 2011

본 논문에서는 디지털통신을 위한 새로운 3차원 16진 신호성상도의 설계방법을 제시하고 그 성능을 분석한다. 기존의 성상도와는 달리 새로운 성상도는 모든 신호점들이 구의 표면에 균일하게 분포하므로 상진폭과 대칭적 구조 특성을 동시에 만족한다. 신호성상도의 평균전력을 정규화시킨 경우 제시된 16진 신호성상도는 기존의 비상진폭(non-constant envelope) 성상도들에 비하여 최대 11.4% 가량 증가된 최소 유클리드 거리를 가지는 것으로 나타났다. 이로 인하여 가산성 백색 가우시안잡음 환경에서 제안된 신호성상도가 적용된 디지털 통신시스템의 심볼오율은 기존 성상도를 이용하는 시스템에 비하여 1.2dB 가량 향상됨을 확인할 수 있다. 유클리드 거리 측면에서 최적화된 기존 상진폭 신호성상도에서는 신호점들이 구의 표면에 균일하게 분포하지 않는 반면 새로운 성상도는 3차원 신호공간에서 완전 대칭인 신호점 분포를 가진다. 이와 함께 기존의 성상도에 비하여 제안된 성상도에서는 설계에 요구되는 연산복잡도가 거의 없는 장점도 있다. 따라서 제안된 3차원 16진 신호성상도는 편광편이키잉과 같이 상진폭 특성이 요구되는 디지털 통신시스템에 적합한 것으로 판단된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.183-186
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• 1991

In order to prepare the functional organic optic meterials, the capacitive coupled gas flow type plasma polymerization apparatus was designed and manufactured. Styrene and para-Xylene monomer were adopt as organic materisl. Optical constant, refrative index, extinction coefficient of organic thin films by the gas flow type plasma polymerization appratus were determined by envelope method using spectrophotometry. The refractive index of plasma polymerized thin films was decreased in accordance to increase of wave length and discharge time. The extinction coefficient was very small compared with refractive index. From the experimental result of optical constant and film thickness, it was considered that the films which had required optical properties and thickness can be prepared by control of polymerization condition.

• 한국통신학회논문지
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• 제30권9A호
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• pp.795-802
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• 2005

바이너리 CDMA(B-CDMA) 기술은 CDMA 신호의 크기를 일정하게 유지시키는 새로운 변조 기법이다. 다중코드CDMA 신호를 일정한 레벨의 신호로 양자화한 후 변조함으로써 B-CDMA 기술은 CDMA 신호가 가지는 장점들을 유지하는 동시에 최대전력 대 평균전력의 비율을 감소시킨다. 본 논문에서는 확산인자가 현저히 작지 않은 가정 하에 B-CDMA시스템의 성능을 다중 경로 페이딩 환경에서 분석한다. 수학적 분석 결과는 컴퓨터 모의실험을 통하여 검증된다.

• Korean Journal of Mathematics
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• 제7권2호
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• pp.207-213
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• 1999

In this paper we estimate a lower bound of the Banach-Mazur distance between a finite dimensional nonlocally convex space and its Banach envelope space by investigating the properties of the nonlocally convex space and the projection constant which are obtained by factoring the identity operator through $l^k_{\infty}$ on the quasi-normed spaces.

• Journal of Biosystems Engineering
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• 제34권2호
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• pp.82-88
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• 2009

This study was conducted to detect faults in a gearbox comprised of gears, bearings and shafts. The envelope analysis was used as a method of detection, which could detect breakage and pitting of gears and bearings, and misalignment of shafts effectively. Vibration measured at the increaser was analyzed to characterize the faults. When the increaser has a defect, peaks with a constant period appear in the time history of vibration and its harmonic components also in the envelope spectrum. The envelope analysis showed that a crack in the stepped output shaft caused the increaser to generate the abnormal peaks.